MIZUHO
Rose-Kit series
1W CW QRP
7 / 21 MHz Transmitter Kit
MODEL QP-7
QP-21
¥3,000 ASSEMBLY MANUAL
Easy Construction
Building your own transmitter is exciting and much
more satisfying than using
commercially-made "luxury" units.
In the days of many high-power stations, 1W QRP
is a lot of fun! QP-7 is a
mini-transmitter, made by Mizuho for your
enjoyment. It is a CW transmitter,
but you can convert it to AM easily, by adding a
modulator.
This kit contains all necessary parts and the PCB. It
is called the "BARA"
kit, which stands for "rose" in Japanese.
Circuit
The transmitter contains 3 stages (see block
diagram in fig. 1 and schematics
in fig. 2):
1. Crystal Oscillator
A 7 MHz crystal oscillates in a Pierce-type
oscillator circuit.
2. Buffer/Amplifier
This stage isolates the oscillator from the power
amplifier and the antenna.
3. Power Amplifier
This stage amplifies the signal from the
oscillator to a higher level. Output is around one (1)
watt. A 5-element low-pass harmonic filter on the
collector of the final transistor attenuates
undesirable harmonics and assures proper
matching to the antenna load. The final transistor
is a 2SC1957.
Construction
First inventory all parts and make sure none is
missing. You will also find some small pins. Those
are soldered on the boards as terminals (see fig. 3
for pin placement). When you assemble the kit,
make sure the transistors are oriented correctly, as
described in fig. 4. Resistors are identified by their
color code (fig. 5). You can simplify the assembly
job by pre-sorting the resistors and tacking them on
a copy of the parts list. Capacitors have their values
printed on them. For an example, a 0.01uF
capacitor reads 103, which means 10 x 10**3 or
10,000 pF. For caps smaller than 100pF, the actual
value may be shown instead of the coded value
above. The final transistor Q3 must have a heat
sink. It is tightened to the board with a 3x10 screw,
which is supplied with the kit (see fig. 6). You
should be able to complete the kit assembly within
2 hours.
After you are done, place and solder the pins on the
PCB. You may connect an ammeter to measure the
supply current as shown in fig. 7. Without an
ammeter, you must wire the pins, as shown in the
dotted line in fig. 7. The transmitter will not function
correctly, if you fail to wire the pins!
2. Alignment of the Buffer stage
Connect the RF-probe between the collector of
Q2 (or the base of Q3) and ground. Adjust L2 for
peak readout.
3. Alignment of the Final amplifier stage
Connect the RF-probe across the antenna
terminals. Adjust L3 and L4 for maximum output.
Alternatively, you may use an LED with a single coil
at L4, as shown in fig. 9. Adjust L3 and L4 for
maximum brightness.
Alignment
To perform the alignment procedure, you need an
RF-meter. Alternatively you can use a home-built
RF-probe (see fig. 8), attached to a DC voltmeter.
Set the voltmeter to the lowest range during these
measurements. We recommend that you use an
insulated tool for adjusting L1 and L2. Connect a 50
ohm / 2W load (51 ohm resistor is OK) across the
antenna terminals. apply power and key-down the
transmitter. It is best to monitor the supply current
while you first apply power. Any excessive current
is an indication of a problem in the construction.
1. Alignment of the Oscillator stage
Connect the RF-probe between the collector of
Q1 and ground. Adjust L1 for maximum signal
readout.
4. Now tweak L1 and L2 again for maximum output.
You have just completed the alignment of your
transmitter! Key-down and monitor the signal on a
good receiver. You will still detect a carrier tone
with key up, since Q1 oscillator is free-running. This
is not a problem during a QSO.
Note : Combine L4 and LED with one-turn coil. And
adjust L3, L4 cores as LED will light brightly. After
that, adjust through L1 to L4 as LED to be brightest
Note : Prepare the current meter for DC. If you will
not use the meter, connect each terminals as per
dotted lines (short-circuit). Accordingly, 0.01uF
condenser will be not necessary.
Note: keep wiring short (1.0-1.5"). The RF-probe
wiring may be longer, provided the rectifier circuit
(fig. 8) is very close to the actual
circuit.
power supply to the transmitter and the antenna,
when using this transmitter in combination with a
receiver. a DPDT (double-pole double-throw)
switch, which is a two-circuit dual position switch
will do the job (see fig. 10 for details). You may
need to use a more complicated scheme to activate
the transmit, while the receiver is on (for
zero-beating). Fig. 11 shows the transmitter, as it
used with a commercial receiver. Use the MUTE
capability of a communications receiver when
transmitting. If you are using a transceiver for
reception, you may have to use the PTT to mute its
receiver. For a tube-type transceiver, just turn off
the heater to the final stage. Some solid-state
radios allow turning down power to zero. You may
also set your transceiver is a "split" mode, with
transmit out-of-band. Check with your owner's
manual, to make sure the transceiver will mute in
this configuration, when PTT is applied. If you use a
short wave receiver, you may have to turn off the
external power
while transmitting, as shown in fig. 12.
Other Applications
Enthusiasts of AM-phone may add a modulator to
this transmitter, as shown in fig. 13. Modulating this
1W transmitter is a "light" task, and can be applied
Attaching a receiver
You will need a "Standby Switch" for switching the
at the collector of the final transistor Q3. You can
also apply modulation to the buffer/amp stage. The
lower level signal may be obtained from a tap in the
modulation transformer. Nowadays, you may think
there aren't many AM stations on the 7 or 21 MHz
bands. You may still communicate with your AMphone transmitter, and if anybody complains about
"too much carrier old man", you may answer "not
really, it's an AM-phone transmitter" and enjoy the
surprise of the other operator mumbling something
like "Wow! This is my first AM-phone QSO!!!"
Note that the crystal supplied with the kit is for the
CW portion of the band. You will need to purchase
a suitable crystal to operate this transmitter on
phone. Mizuho also offers a "VFO-7" kit for the QP7 and QP-21 transmitters.
QP-7,21 Parts Table
check
parts id
Parts QP-7 Parts QP-21
PIN terminal
E
num. Reference
14 figure-3
L1,L2 Mizuho coil SL-113 Mizuho coil SL-111 2 case sielded
L3,L4 Mizuho coil SL-95 Mizuho coil SL-96 2 8mm dia coil
CH1 Mizuho SL-15
Q1 2SC945
Q2 2SC1959
Q3 2SC1957
Socket for crystal
E
E
E
E
E
1 5mm dia coil
1
1
1 figure-6 to install
1 HC-25U type
Crystal1 Crystal 7025KHz Crystal 21135kHz 1 use socket
R1 22K-Ohm 1/4W
R2,5 4.7K
R3,4 1K
R6 10K
R7,8 100-Ohm
R9 22
R10 470
C1 capacitor 0.001uF
C2,4,8,
0.01uF
E
E
E
E
E
E
E
E
E
1 red-red-org
2 yel-pur-red
2 brn-blk-red
1 brn-blk-org
2 brn-blk-brn
1 red-red-blk
1 yel-pur-brn
1 “102”
5 “103”
10,11
C3 15pF
C5 150pF
E
E
1 15
2 “151”
C6 68pF 33pF 1 68 or 33
C7 10uF 16V
E
1 10uF
C9 15pF 39pF
C12 0.047uF 0.001uF 1 “473” or “102”
C13 330pF 47pF 2 “331” or “47”
C14 330pF 180pF
C15 180pF 150pF 1 “181” or “151”
circuit board
51-ohm resistor
LED with one-turn
spacer
3mm ISO bolt
spring washer
nut
soider wire
E
E
E
E
E
E
E
E
1
1 for alignment
1 for alignment
2 for installation
2 for installation
2 for installation
2 for installation
You can pass the authorized transmitter inspection of JARL as for 10W station
if you submit the block diagram of QP-7(21).
This manual is voluntary translated by JA-QRPers.
This is not the official documentation of MIZUHO corporation.
1998/04/22 Version 2.1 JO1ACW, JE2CDC, JN2FSE, JL1KRA (tnx to AC6AN)
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